Tethys is participating in an exploration well, B4EW4 on Block 4 onshore Oman which has started drilling. The well is located outside the 3D seismic area approximately 20 km west of the Saiwan East Oilfield. The well will target five potential reservoir formations, four of which are proven hydrocarbon bearing reservoirs in other locations in Oman.

The well is planned to be drilled to a total measured depth of 3,300 metres and targets the Lower Al Bashir, Miqrat, Amin, Buah and Masirah Bay formations. The Lower al Bashir sandstone formation is in production on Block 3. The Miqrat and Amin sandstone formations and the Buah carbonate formation have all been proven to be hydrocarbon bearing in other wells on the license, and all three formations are in production on other locations in Oman (gas and conventional oil). The Masirah Bay sandstone formation has never been proven.

Tethys Oil AB, through its wholly owned subsidiary Tethys Oil Block 3 and 4 ltd, has a 30 per cent interest in Blocks 3 and 4. Partners are Mitsui E&P Middle East B.V. with 20 per cent and the operator CC Energy Development S.A.L. (Oman branch) holding the remaining 50 per cent.